Referring to FIG. 1, a conventional multi-output DC-to-DC power converter 1 is shown to include a transformer (T1), a primary side control circuit 11, first to third rectifier and filter circuits 12, 13, 14, a regulator circuit 15, a feedback circuit 16 and a regulator control circuit 17.
The transformer (T1) has a primary winding (Lp) and first to third secondary windings (Ls1, Ls2, Ls3). The primary side control circuit 11 is used to receive a DC input voltage (Vin) from an input power source 10, and is coupled to the primary winding (Lp) of the transformer (T1). The primary side control circuit 11 controls supply of the DC input voltage (yin) to the primary winding (Lp). When the DC input voltage (Vin) is supplied to the primary winding (Lp), the transformer (T1) generates first to third induced voltages respectively across the first to third secondary windings (Ls1, Ls2, Ls3). The first rectifier and filter circuit 12 is coupled to the first secondary winding (Ls1) of the transformer (T1) for receiving the first induced voltage therefrom, and rectifies and filters the first induced voltage so as to output a first DC output voltage (V1) of 12V to a load (not shown). The second rectifier and filter circuit 13 is coupled to the second secondary winding (Ls2) of the transformer (T1) for receiving the second induced voltage therefrom, and rectifies and filters the second induced voltage so as to output a second DC output voltage (V2) of 5V to a load (not shown). The third rectifier and filter circuit 14 is coupled to the third secondary winding (Ls3) of the transformer (T1) for receiving the third induced voltage therefrom, and rectifies and filters the third induced voltage so as to output a third DC output voltage (V3). The regulator circuit 15 is coupled to the third rectifier and filter circuit 14 for receiving the third DC output voltage (V3) therefrom. The regulator circuit 15 regulates the third DC output voltage (V3) based on a control signal to generate a regulated third DC output voltage (V3′), and outputs the regulated third DC output voltage (V3′) of 3.3V to a load (not shown). The feedback circuit 16 is coupled to the regulator circuit 15 for receiving the regulated third DC output voltage (V3′) therefrom, and generates a feedback signal based on the regulated third DC output voltage (V3′). The regulator control circuit 17 is coupled to the regulator circuit 15 and the feedback circuit 16. The regulator control circuit 17 receives the feedback signal from the feedback circuit 16, generates the control signal based on the feedback signal, and outputs the control signal to the regulator circuit 15.
Under such configuration, it is evident that to output a plurality of different DC output voltages, the conventional multi-output DC-to-DC power converter 1 must include a plurality of different secondary windings respectively for the different DC output voltages, and a plurality of rectifier and filter circuits that are coupled respectively to the secondary windings. In this way, the number of the secondary windings (Ls1, Ls2, Ls3) of the transformer (T1) is increased, and the circuitry of the transformer (T1) becomes more complicated. Therefore, the manufacturing cost and the volume of the transformer (T1) are both increased.